[解决方案] Ubuntu 16.04 下 Qt 5.6 无法输入中文的问题

0. 环境

系统：ubuntu 16.04 LTS
机子：dell xps13

1. 步骤

1.1 编译 fcitx-qt5 源码

1. 编译fcitx-qt需要cmake，安装cmake命令，如果已经安装，请略过;
   sudo apt-get install cmake
2. 安装 fcitx-libs-dev;
   sudo apt-get install fcitx-libs-dev
3. 设置qmake的环境变量，这一步很重要且环境变量的值因人而异
   3.1. 首先确定你的Qt的安装目录，我这里是~/software/Qt5.6.0/，你的或者可能在/home/<用户名>/Qt5.6.0/
   3.2. export PATH="<Qt安装目录>/5.6/gcc_64/bin":$PATH
4. 下载fcitx-libs 源码
   4.1. 原文的 git clone git@github.com:fcitx/fcitx-qt5.git 不可行，需要修改为 https://github.com/fcitx/fcitx-qt5
   4.2. git clone https://github.com/fcitx/fcitx-qt5
5. 编译 fcitx-qt5

cd fcitx-qt5
cmake .
make 
sudo make install

1.2. 拷贝 so 文件

1. 编译完成后，需要把编译得到的 libfcitxplatforminputcontextplugin.so 拷贝到 Qt5.5 安装目录的 Tools/QtCreator/bin/plugins/platforminputcontexts 或 Qt5.6 安装目录的 Tools/QtCreator/lib/Qt/plugins/platforminputcontexts，注意：两个目录根据你的Qt版本而定，Qt安装目录因人而异。
2. 复制：
   Qt 5.5：cp platforminputcontext/libfcitxplatforminputcontextplugin.so <Qt安装目录>/Tools/QtCreator/bin/plugins/platforminputcontexts
   Qt 5.6：cp platforminputcontext/libfcitxplatforminputcontextplugin.so <Qt安装目录>/Tools/QtCreator/lib/Qt/plugins/platforminputcontexts
   我这里是：cp platforminputcontext/libfcitxplatforminputcontextplugin.so ~/software/Qt5.6.0/Tools/QtCreator/lib/Qt/plugins/platforminputcontexts

1.3 添加额外的环境变量

echo 'export XMODIFIERS=@im=fcitx' >> .bashrc 
echo 'export QT_IM_MODULE=fcitx' >> .bashrc

大功告成！

2. 遇到的问题

说明：本人系统为 Ubuntu 16.04 LTS 英文版 ，遇到的问题基本和原文一样

2.1 安装CMake失败

1. 问题描述：sudo apt-get install cmake 执行到 92 % 时提示下载失败，原因是找不到 IP 地址。
2. 问题解决：觉得应该是安装包源的问题，于是修改了系统默认的源。
   System Settings -> Software & Updates -> Ubuntu Software -> Download from 从原来的 China 改为 Main server，最后再
   sudo apt-get update
sudo apt-get install cmake

2.2 CMake 错误

1. 问题描述：

CMake Error at CMakeLists.txt:8 (find_package):
Could not find a package configuration file provided by "ECM" (requested
  version 1.4.0) with any of the following names:
    ECMConfig.cmake
    ecm-config.cmake
  Add the installation prefix of "ECM" to CMAKE_PREFIX_PATH or set "ECM_DIR"
  to a directory containing one of the above files.  If "ECM" provides a
  separate development package or SDK, be sure it has been installed.
-- Configuring incomplete, errors occurred!

2. 解决方法：
   2.1. 到这个页面 https://launchpad.net/ubuntu/+source/extra-cmake-modules/1.4.0-0ubuntu1 下载 extra-cmake-modules_1.4.0.orig.tar.xz
   2.2. 解压后编译安装

cd extra-cmake-modules-1.4.0
cmake .
make
sudo make install

2.3 安装 extra-cmake-modules-1.4.0 失败

1. 问题描述：

$:~/Downloads/extra-cmake-modules-1.4.0$ cmake .
CMake Warning at tests/CMakeLists.txt:28 (find_package):
  Could not find a package configuration file provided by "Qt5LinguistTools"
  with any of the following names:
    Qt5LinguistToolsConfig.cmake
    qt5linguisttools-config.cmake
  Add the installation prefix of "Qt5LinguistTools" to CMAKE_PREFIX_PATH or
  set "Qt5LinguistTools_DIR" to a directory containing one of the above
  files.  If "Qt5LinguistTools" provides a separate development package or
  SDK, be sure it has been installed.
-- Looking for Sphinx Documentation Builder...
-- Sphinx Documentation Builder not found - documentation will not be built (see http://sphinx-doc.org/)
-- Configuring done
-- Generating done
-- Build files have been written to: /home/cposture/Downloads/extra-cmake-modules-1.4.0

2. 解决方法：
   设置 CMAKE_PREFIX_PATH 环境变量 为 qtbase 目录（<Qt安装目录>/5.6/Src/qtbase/），我这里为：

export CMAKE_PREFIX_PATH="~/software/Qt5.6.0/5.6/Src/qtbase/"

如果还是不行，则修改为

export CMAKE_PREFIX_PATH="/home/cposture/software/Qt5.6.0/5.6/gcc_64/lib/cmake/"

2.4 缺少 xkbcommon 包

1. 问题描述：

 -- Found PkgConfig: /usr/bin/pkg-config (found version "0.26") 
-- Could NOT find XKBCommon_XKBCommon (missing:  XKBCommon_XKBCommon_LIBRARY XKBCommon_XKBCommon_INCLUDE_DIR) 
CMake Error at /usr/share/cmake-2.8/Modules/FindPackageHandleStandardArgs.cmake:108 (message):
  Could NOT find XKBCommon (missing: XKBCommon_LIBRARIES XKBCommon) (Required is at least version "0.5.0") 

2. 解决方法：
   2.1. 到 http://xkbcommon.org/ 下载最新版的 xkbcommon
   2.2. 解压后，

sudo apt-get install bison
./configure --prefix=/usr --libdir=/usr/lib/x86_64-linux-gnu --disable-x11
make
sudo make install

原文链接：http://www.cnblogs.com/cposture/p/5397694.html
参考：http://my.oschina.net/lieefu/blog/505363?p=1